1. Technical Field
The disclosed embodiments relate generally to frequency dividers, including high-speed frequency dividers operable in wireless communication systems.
2. Background Information
State-of-the-art divide-by-three circuits for Radio Frequency (RF) transceivers of cellular telephones are typically designed in a single-ended fashion. Such single-ended designs have several disadvantages. In one example, they have a poor power-supply rejection that results in poor isolation between a transmit signal path (Tx) and a receive signal path (Rx). Because of this poor Tx-to-Rx isolation, downconverted receive signals may be corrupted (and the receiver's signal-to-noise ratio degraded), and phone calls may be lost. In order to drive state-of-the-art double-balanced mixers, differential quadrature Local Oscillator (LO) signals are generated by inverting the divider output signals. The differential signals generated may be unbalanced as they undergo different physical paths (with different delays that are hard to control). This creates a strong common-mode component at the output of the mixer that degrades the receiver's second-order input-intercept point (IIP2) and signal-to-noise ratio accordingly. In another example, divide-by-three circuits may fail when operating in certain frequency ranges.